For the summer the destination I am going to has humid subtropical climate and 20 C to 28 C temperatures for a normal day. How can I pack only with a S-size suitcase so that can I buy essentials there and additional clothes if I’ll be needing them.

I have travelled before, but I am really bad at packing and literally spend days overthinking things, like should I pack this or that.

For example, I am not going to pack a toothbrush and toothpaste since I can buy that for cheap in a supermarket there already

For clothes, the only personal downside is that I don’t like showing skin since it’s not comfortable for me (mainly because I have back acne). But I am working towards that

I would appreciate if you could help me with packing strategies